Efficiency improvement by using metal-insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

Area of Science:

• Semiconductor Physics
• Optoelectronics
• Materials Science

Background:

• Micro-light-emitting diodes (micro-LEDs) are crucial for advanced display technologies.
• Efficiency limitations in InGaN/GaN micro-LEDs hinder widespread adoption.
• Surface recombination is a significant factor affecting micro-LED performance.

Purpose of the Study:

• To propose and investigate a novel metal-insulator-semiconductor (MIS) structure on the sidewall of InGaN/GaN micro-LEDs.
• To enhance the external quantum efficiency (EQE) of micro-LEDs.
• To understand the underlying mechanisms controlling EQE in MIS micro-LEDs.

Main Methods:

• Fabrication of InGaN/GaN micro-LEDs with sidewall MIS structures.
• Electroluminescence (EL) measurements on micro-LEDs with varying sidewall electrode biases.
• Band structure analysis to elucidate the impact of electric fields on surface recombination.

Main Results:

• Application of negative bias to the sidewall electrode significantly increased EQE in 10 μm diameter devices.
• Positive bias on the sidewall electrode led to a decrease in EQE.
• Band structure analysis confirmed that sidewall electric fields modulate surface electron density and control Shockley-Read-Hall (SRH) recombination.

Conclusions:

• The sidewall MIS structure offers a viable pathway to improve InGaN/GaN micro-LED efficiency.
• Controlling surface recombination via electric field modulation is key to enhancing EQE.
• Future improvements can be achieved by reducing insulator thickness and exploring alternative materials.